How to Export Verilog/VHDL from Logisim-evolution

Your schematic is already a hardware description — Logisim-evolution can translate it into real VHDL or Verilog through the built-in FPGA Commander. This is the bridge between the simulator and the professional FPGA workflow: generate the HDL here, synthesize it in your board vendor’s toolchain.

Before you start: HDL prerequisites

The HDL generator is pickier than the simulator. Check these first, or generation will fail with an error dialog:

  • Label everything. Every component needs a valid, unique label. Use the Commander’s Annotate button to auto-label the whole design — “Label only the components without a label or with an invalid label” is the safe choice.
  • No tri-state drivers or floating outputs. They have no meaning in the generated HDL.
  • No gated clocks. Every clocked component must connect to a proper clock net.
  • Valid names. Circuit and sheet names may only contain letters, numbers, and underscores.
  • Stick to supported components. Exotic or custom parts may report “not supported for HDL generation”.

Step-by-step export

Step 1 — Open FPGA Commander. With your top-level circuit open, go to FPGA → FPGA Commander (the dialog title reads “Synthesize & Download…”).
Step 2 — Choose your HDL. Set the hardware description language to VHDL or Verilog, depending on what your toolchain or course expects.
Step 3 — Map inputs and outputs. Connect each top-level pin of your circuit to a board resource (or leave the board mapping minimal if you only want the HDL files — the mapping table still needs sane entries to pass the design-rule check).
Step 4 — Click “Generate HDL only”. This writes the HDL files without attempting a board download. Perfect when you just want the code.

What the generated files look like

Be honest with yourself here: the output is a structural netlist — one entity/module per circuit, with your gates and wires translated into component instantiations. It is correct and synthesizable, but it will not look like hand-written RTL. Reading through it once is genuinely educational: it shows exactly what your schematic means in hardware terms.

Common errors

  • “Found one or more components without a label” → press Annotate in the Commander.
  • “Duplicated labels” → make labels unique (Annotate fixes this too).
  • “Tri-state driver or floating output” → find the floating pin and tie or remove it.
  • “Gated clock connection” → rework the clocking to a single clean clock.
Put the generated HDL on real silicon
The natural next step after exporting: synthesize it for an FPGA board and watch your simulation become hardware.
Check the Basys 3 price

As an affiliate partner, we may earn a commission on qualifying purchases — at no extra cost to you.

Go further

See the full board workflow in From Simulation to Real Hardware, or analyze timing first with the chronogram.